Problem: Simplify the following expression: ${-a-4(-4a-7)}$
Explanation: Distribute the ${-4}$ into the parentheses: $ -a {-4(}\gray{-4a-7}{)} $ $ -a + {16a+28} $ Combine the $a$ terms: $ {-a + 16a} + 28$ $ {15a} + 28$ The simplified expression is $15a+28$